According to Lambert and MacDonald in their 1998 monograph titled “Reinforced Concrete History, Properties & Durability” (published by the Corrosion Prevention Association, Surrey, U.K.), the oldest known surviving concrete is to be found in the former Yugoslavia and was thought to have been laid in 5,600 BC using red lime as the cement. The first major concrete users were the Egyptians in around 2,500 BC and the Romans from 300 BC. The Romans found that by mixing a pink sand-like material which they obtained from Pozzuoli with their normal lime-based concretes they obtained a far stronger material. The pink sand turned out to be fine volcanic ash and they had inadvertently produced the first pozzolanic' cement. Pozzolana is any siliceous or siliceous and aluminous material which possesses little or no cementitious value in itself but will, if finely divided and mixed with water, chemically react with calcium hydroxide to form compounds with cementitious properties.
The Romans made many developments in concrete technology including the use of lightweight aggregates as in the roof of the Pantheon, and embedded reinforcement in the form of bronze bars, although the difference in thermal expansion between the two materials produced problems of spalling. It is from the Roman words ‘caementum’ meaning a rough stone or chipping and ‘concretus’ meaning grown together or compounded, that we have obtained the names for these two now common materials. Since the Romans had no powered cement mixers, they prepared small batches of concrete, and layered these batches either between wooden forms, or between facings of stone or brick already assembled. The Roman practice of pouring liquid concrete into wooden forms was rediscovered by the architect Bramante in the 15th century A.D., and incorporated into his early work on the Cathedral of St. Peter in Rome.
The use of concrete forms continued to progress, with important developments including iron-reinforced structures in the 18th century and steel-reinforced concrete as a building material of the mid-19th century. Reinforced concrete is often used in the construction of foundation footings, which provide a base for the foundation of a structure. Footings are typically fabricated by placing opposed form elements, spaced 8″-48″ apart, around the design perimeter of the structure below the frostline. Form elements are usually elongate, and can be provided as removable wood or steel planks or permanently-installed foraminous drain elements. When planks are used, dimensional lumber, ranging from 1×4's and 2×4's through 1×12's and 2×12's, are often used for this purpose. The planks are usually secured together by a series of braces, such as 1×2's, to maintain the planks at a consistent distance from one another. Rebar or other reinforcing materials, such as mesh, can be secured within the form. Once the form is ready, concrete is poured to a desired depth and allowed to cure, after which the forms are removed.
Not surprisingly, various supports for concrete forms and associated systems have found their way into the patent literature. For example, U.S. Pat. No. 5,224,799 to Parker is directed to a permanently-installed form-drain including hollow, foraminous planks and connectors for joining two or more of the planks in a continuously arranged concrete barrier. The instant improvements include an adapter, which serves as a straight connector, grooved plank with interlocking stake, integral connector-stake and adapter-stake device and a tri-functional, generally rigid bracket and bracket-stake element, used to space and restrain/constrain the planks and/or to hold (support) reinforcement bars.
U.S. Pat. No. 6,314,697 to Moore sets forth a connector link component for use in an insulated concrete form system having first and second side panels and at least two connectors, each side panel having an exterior surface, an opposed interior surface, and at least one attachment coupling, the panels arranged in spaced parallel relationship with their interior surfaces and attachment couplings facing each other so that a cavity is formed therebetween, each connector having a first end and a distal second end, a first length extending therebetween, and a pair of opposed connector couplings, one connector coupling formed in the first end and the other connector coupling formed in the second end, so that the each connector coupling of each connector is adapted to engage one attachment coupling of the side panel, the connector link having a proximal end, having a first link coupling for engagement to the connector coupling of one connector of the concrete form system, a distal end, having a second link coupling for engagement to the connector coupling of one other connector of the concrete form system, and a substantially rigid body portion extending between the proximal end and the distal end of the connector link so that the connector link may be operatively engaged to the opposed connectors to structurally connect one attachment coupling on one side panel to one other attachment coupling on the other side panel.
U.S. Pat. No. 5,992,114 to Zelinsky deals with an apparatus for providing to an insulated, poured concrete wall which will result, when the concrete is poured, in a wall having internal and external insulation, drywall or other surface preparation connecting areas which are continuous of and extending the entire or selected lengths of the wall and apparatus for the provision of windows into the wall. The apparatus includes a pair of U-shaped lower members attachable to foundation footings to establish the sides of the wall and receive insulating or other material panels, a plurality of H-shaped intermediate members to receive insulating or other material panels which form the pouring area, a pair of U-shaped top members capping the uppermost tier of insulating or other material panels which members may also be utilized to form window openings, a plurality of tie bars frictionally attachable to the H members which provide cross connectors between tiers of the panel sections and U-shaped, corner members for both the bottom and top of the wall.
In U.S. Pat. No. 5,937,604 to Bowron, a concrete forms wall spacer is provided in the configuration of a truss having top and bottom horizontal frame members interconnected by angularly extending reinforcing struts. The top frame member is configured to rest upon the upper edges of a pair of spaced concrete form walls, and end portions of the top frame member are extended downward for abutment by the outer sides of the spaced concrete form walls, to define the desired spacing between the walls. Supported by the bottom frame member are a pair of spaced clip members each configured to removably support a pair of lengths of rebar which extend horizontally in opposite directions to other longitudinally spaced form wall spacers. A pair of vertically spaced rebar supports are mounted on the top and bottom frame members for frictionally securing a vertically extending length of rebar for forming a structural tie between a concrete footing and a vertically extending concrete wall. In a second embodiment of the invention, a plurality of pairs of vertically spaced rebar supports for vertical rebar are provided as detachable components.
U.S. Pat. No. 5,399,050 to Jacobus is directed to a thermoplastic sidewall forming one surface of a concrete form. The sidewall incorporates a drainage tile as an integral unit. Two of the sidewalls combined can provide a form for a concrete footer to be poured and remain as a permanent part of the structure.
U.S. Pat. No. 5,065,561 to Mason deals with a concrete wall form system including a plurality of first and second panels each preferably having grooved portions extending along corresponding top side edges and complementary mating tongue portions extending along corresponding bottom side edges, and having regularly spaced transverse slots extending into the top and bottom side edges thereof The form system also includes a plurality of ties each having a bridging web portion, interior flanges formed at the opposite extremities of the web portions, and fastening portions also formed at each end of the web portion and including an outwardly extending shank terminating in an outer flange, the shanks of the fastening portions being adapted for disposition in the aligned transverse slots in vertically adjacent form panels, the interior flanges engaging an interior wall of the panels, and the exterior flanges engaging an outer side wall of the panels. In accordance with the present invention each horizontal row of ties holds together both the top edges of one course of panels and the bottom edges of another course of panels disposed immediately thereabove.
It can thus be seen from the foregoing that several attempts have been made to provide structural reinforcements for concrete forms, some of which address the problem of retaining rebar within the form. The patent to Parker, in particular, shows dimpled grooves in which rebar may be constrained or retained. Unfortunately, none of the known apparatus provide for positive retention of reinforcing materials. Consequently, reinforcing material such as rebar is subject to undesirable movement either before or during the concrete pour. Improper concrete reinforcing can lead to failure of the completed structure. Clearly, the need exists for a simple, inexpensive mechanism associated with a form brace for positively retaining reinforcing materials within a concrete form without diminishing the effectiveness of the functionality of the brace itself.
All patents, patent applications, provisional patent applications and publications referred to or cited herein, are incorporated by reference in their entirety to the extent they are not inconsistent with the teachings of the specification.